Brown Automatic Signaling Pyrometer

In large heat-treating plants it has been customary to maintain
an operator at a central pyrometer, and by colored electric lights
at the furnaces, signal whether the temperatures are correct or
not. It is common practice to locate three lights above each
furnace-red, white and green. The red light burns when the temperature
is too low, the white light when the temperature is within certain
limits--for example, 20 deg.F. of the correct temperature--and the
green light when the temperature is too high.

Instruments to operate the lights automatically have been devised and
one made by Brown is shown in Fig. 130. The same form of instrument is
used for this purpose to automatically control furnace temperatures,
and the pointer is depressed at intervals of every 10 sec. on contacts
corresponding to the red, white and green lights.